U.S. patent number 8,552,704 [Application Number 13/080,017] was granted by the patent office on 2013-10-08 for current share compensation design.
This patent grant is currently assigned to Maxim Integrated Products, Inc.. The grantee listed for this patent is Stewart Gall Kenly, Mansur Kiadeh, Paul Walker Latham, II, Maria-Silvia Ratto, Paolo Luigi Tronconi. Invention is credited to Stewart Gall Kenly, Mansur Kiadeh, Paul Walker Latham, II, Maria-Silvia Ratto, Paolo Luigi Tronconi.
United States Patent |
8,552,704 |
Kiadeh , et al. |
October 8, 2013 |
Current share compensation design
Abstract
A current share system for providing current to a load includes
a first power supply module that controls a first voltage converter
to provide a first current to the load, that transmits
synchronization information using a first pin, and that transmits
at least one second type of information using the first pin. A
second power supply module receives the synchronization information
at a second pin, receives the at least one second type of
information at the second pin, and controls a second voltage
converter to provide a second current to the load based on the
synchronization information and the at least one second type of
information.
Inventors: |
Kiadeh; Mansur (Cupertino,
CA), Latham, II; Paul Walker (Lee, NH), Ratto;
Maria-Silvia (Trezzano, IT), Tronconi; Paolo
Luigi (Rozzano, IT), Kenly; Stewart Gall (Epping,
NH) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kiadeh; Mansur
Latham, II; Paul Walker
Ratto; Maria-Silvia
Tronconi; Paolo Luigi
Kenly; Stewart Gall |
Cupertino
Lee
Trezzano
Rozzano
Epping |
CA
NH
N/A
N/A
NH |
US
US
IT
IT
US |
|
|
Assignee: |
Maxim Integrated Products, Inc.
(San Jose, CA)
|
Family
ID: |
46965607 |
Appl.
No.: |
13/080,017 |
Filed: |
April 5, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120256659 A1 |
Oct 11, 2012 |
|
Current U.S.
Class: |
323/285;
363/72 |
Current CPC
Class: |
H02M
3/1584 (20130101) |
Current International
Class: |
G05F
1/40 (20060101) |
Field of
Search: |
;323/222,224,266-267,272,275,282-290
;363/16-17,21.02,21.18,41,61,65,89,98,132
;307/43,64-66,52,67,105,102,110 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Zhang, Y. et al., "Current Sharing in Digitally Controlled
Masterless Multi-phase DC-DC Converters", Power Electronics
Specialists Conference, Jun. 2005, PESC '05 IEEE 36th,
10.1109/PESC.2005.1582018, pp. 2722-2728. cited by applicant .
Ozkaynak, I., "Modeling and Design of n+1 Current Share as
Disturbance Rejection for DC-DC Converters", 2005, Senior Member
IEEE Power Supply Consultants. cited by applicant .
Panov, Y. et al., "Loop Gain Measurement for Paralleled DC-DC
Converters With Average-Current-Sharing Control", 2008, IEEE
Transactions on Power Electronics. vol. 23, No. 6., pp. 2942-2948.
cited by applicant .
Lin, C S. et al., Single-Wire Current-Share Paralleling of
Current-Mode Controlled DC Power Supplies, 2000, IEEE Transaction
on Industrial Electronics, vol. 47., No. 4, pp. 780-786. cited by
applicant.
|
Primary Examiner: Patel; Rajnikant
Claims
What is claimed is:
1. A current share system for providing current to a load, the
current share system comprising: a first power supply module that
controls a first voltage converter to provide a first current to
the load, that transmits synchronization information using a first
pin, and that transmits at least one second type of information
using the first pin; and a second power supply module that receives
the synchronization information at a second pin, that receives the
at least one second type of information at the second pin, and that
controls a second voltage converter to provide a second current to
the load based on the synchronization information and the at least
one second type of information.
2. The current share system of claim 1 wherein a digital signal
includes the synchronization information and the at least one
second type of information.
3. The current share system of claim 1 wherein the second type of
information includes at least one of current sharing information,
duty cycle information, and commands.
4. The current share system of claim 1 wherein the second type of
information includes duty cycle information, and wherein the second
power supply module adjusts a duty cycle of the second voltage
converter based on the duty cycle information.
5. The current share system of claim 1 wherein the synchronization
information includes synchronization pulses and the second type of
information includes a frame of data.
6. The current share system of claim 5 wherein the frame of data is
transmitted between consecutive ones of the synchronization
pulses.
7. The current share system of claim 1 wherein: the at least one
second type of information includes current sharing information
corresponding to the first current; and the second power supply
module receives the current sharing information, receives a signal
corresponding to the second current, and adjusts the second current
based on the current sharing information and the signal.
8. The current share system of claim 7 wherein the second power
supply module adjusts the second current further based on an output
stage resonance frequency of the current share system.
9. The current share system of claim 7 wherein the second power
supply module includes a proportional-integral (PI) control module
that adjusts the second current, and wherein a proportional gain of
the PI control module is selected such that a zero of the PI
control module matches an output stage resonance frequency of the
current share system.
10. The current share system of claim 9 wherein an integral gain of
the PI control module is set to 1.
11. A method for operating a current share system for providing
current to a load, the method comprising: using a first power
supply module, controlling a first voltage converter to provide a
first current to the load; transmitting synchronization information
using a first pin of the first power supply module; transmitting at
least one second type of information using the first pin; receiving
the synchronization information at a second pin of a second power
supply module; receiving the at least one second type of
information at the second pin; and using the second power supply
module, controlling a second voltage converter to provide a second
current to the load based on the synchronization information and
the at least one second type of information.
12. The method of claim 11 wherein a digital signal includes the
synchronization information and the at least one second type of
information.
13. The method of claim 11 wherein the second type of information
includes at least one of current sharing information, duty cycle
information, and commands.
14. The method of claim 11 wherein the second type of information
includes duty cycle information, and wherein the second power
supply module adjusts a duty cycle of the second voltage converter
based on the duty cycle information.
15. The method of claim 11 wherein the synchronization information
includes synchronization pulses and the second type of information
includes a frame of data.
16. The method of claim 15 further comprising transmitting the
frame of data between consecutive ones of the synchronization
pulses.
17. The method of claim 11 wherein the at least one second type of
information includes current sharing information corresponding to
the first current, and further comprising: receiving the current
sharing information using the second power supply module; receiving
a signal corresponding to the second current using the second power
supply module; and adjusting the second current based on the
current sharing information and the signal using the second power
supply module.
18. The method of claim 17 further comprising adjusting the second
current further based on an output stage resonance frequency of the
current share system using the second power supply module.
19. The method of claim 17 wherein the second power supply module
includes a proportional-integral (PI) control module, and further
comprising: adjusting the second current using the PI control
module; and selecting a proportional gain of the PI control module
such that a zero of the PI control module matches an output stage
resonance frequency of the current share system.
20. The method of claim 19 further comprising setting an integral
gain of the PI control module to 1.
Description
FIELD
The present disclosure relates to control systems for power
supplies, and more particularly to systems and methods for current
sharing between DC to DC converters.
BACKGROUND
The background description provided herein is for the purpose of
generally presenting the context of the disclosure. Work of the
presently named inventors, to the extent it is described in this
background section, as well as aspects of the description that may
not otherwise qualify as prior art at the time of filing, are
neither expressly nor impliedly admitted as prior art against the
present disclosure.
A power supply outputs a predetermined voltage that may be used to
power one or more components. For example, the predetermined
voltage may power one or more components of an integrated circuit
(IC). In some situations, however, a voltage that is less than the
predetermined voltage may be sufficient. The lower voltage may be
obtained from the predetermined voltage using a voltage divider
circuit. Voltage divider circuits, however, are inefficient and
inaccurate.
The power supply may implement a DC to DC converter (such as a
step-down, or "buck," converter) to provide the lower voltage.
Under a given set of conditions, a buck converter is generally more
efficient and more accurate than a voltage divider circuit. A buck
converter may include an inductor, a capacitor, and two switches.
The buck converter alternates between charging the inductor by
connecting the inductor to the predetermined voltage and
discharging the inductor to a load.
Two or more single phase power supplies may be stacked (i.e.,
provided in parallel) to minimize a required input capacitance,
increase output power, reduce thermal stress, and lower inductor
height. Each of the power supplies provides current during a
respective phase.
SUMMARY
A current share system for providing current to a load includes a
first power supply module that controls a first voltage converter
to provide a first current to the load, that transmits
synchronization information using a first pin, and that transmits
at least one second type of information using the first pin. A
second power supply module receives the synchronization information
at a second pin, receives the at least one second type of
information at the second pin, and controls a second voltage
converter to provide a second current to the load based on the
synchronization information and the at least one second type of
information.
In other features, a digital signal includes the synchronization
information and the at least one second type of information. The
second type of information includes at least one of current sharing
information, duty cycle information, and commands. The second type
of information includes duty cycle information, and the second
power supply module adjusts a duty cycle of the second voltage
converter based on the duty cycle information. The synchronization
information includes synchronization pulses and the second type of
information includes a frame of data. The frame of data is
transmitted using consecutive ones of the synchronization
pulses.
In other features, at least one second type of information includes
current sharing information corresponding to the first current. The
second power supply module receives the current sharing
information, receives a signal corresponding to the second current,
and adjusts the second current based on the current sharing
information and the signal. The second power supply module adjusts
the second current further based on an output stage resonance
frequency of the current share system. The second power supply
module includes a proportional-integral (PI) control module that
adjusts the second current, and a proportional gain of the PI
control module is selected such that a zero of the PI control
module matches an output stage resonance frequency of the current
share system. To simplify the design of the PI controller, an
integral gain of the PI control module is set to 1.
Further areas of applicability of the present disclosure will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples are intended for purposes of illustration only and are not
intended to limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure will become more fully understood from the
detailed description and the accompanying drawings, wherein:
FIG. 1 is a functional block diagram of an example current share
system including DC to DC buck converters according to the present
disclosure;
FIG. 2 is a functional block diagram of an example of current share
system according to the present disclosure;
FIG. 3 is a functional block diagram of an example current share
control module according to the present disclosure; and
FIG. 4 is a flowchart illustrating steps of an example current
share method according to the present disclosure.
DETAILED DESCRIPTION
The following description is merely illustrative in nature and is
in no way intended to limit the disclosure, its application, or
uses. For purposes of clarity, the same reference numbers will be
used in the drawings to identify similar elements. As used herein,
the phrase at least one of A, B, and C should be construed to mean
a logical (A or B or C), using a non-exclusive logical or. It
should be understood that steps within a method may be executed in
different order without altering the principles of the present
disclosure.
As used herein, the term module may refer to, be part of, or
include an Application Specific Integrated Circuit (ASIC); an
electronic circuit; a combinational logic circuit; a field
programmable gate array (FPGA); a processor (shared, dedicated, or
group) that executes code; other suitable components that provide
the described functionality; or a combination of some or all of the
above, such as in a system-on-chip. The term module may include
memory (shared, dedicated, or group) that stores code executed by
the processor.
The term code, as used above, may include software, firmware,
and/or microcode, and may refer to programs, routines, functions,
classes, and/or objects. The term shared, as used above, means that
some or all code from multiple modules may be executed using a
single (shared) processor. In addition, some or all code from
multiple modules may be stored by a single (shared) memory. The
term group, as used above, means that some or all code from a
single module may be executed using a group of processors. In
addition, some or all code from a single module may be stored using
a group of memories.
The apparatuses and methods described herein may be implemented by
one or more computer programs executed by one or more processors.
The computer programs include processor-executable instructions
that are stored on a non-transitory tangible computer readable
medium. The computer programs may also include stored data.
Non-limiting examples of the non-transitory tangible computer
readable medium are nonvolatile memory, magnetic storage, and
optical storage.
Two or more single phase power supplies may be stacked such that
each power supply provides current during a respective phase. In
other words, the power supplies operate in a current sharing mode.
In the current sharing mode, current and power provided to a common
load are shared amongst the power supplies.
Each of the power supplies may have different operating
characteristics that prevent current from being equally shared
amongst the power supplies, resulting in a current imbalance. For
example only, variations in component tolerances, offsets,
environmental conditions, and connections between the power
supplies and the common load may cause variations between the
currents provided in each phase, and consequently cause the current
imbalance.
A current share system of the present disclosure implements a
synchronization (sync) control module that communicates with each
of the power supplies in a current share arrangement. For example
only, one or more of the power supplies may include the sync
control module. One of the power supplies including the sync
control module may be a master power supply module and the
remaining power supplies may be slave power supply modules. The
master power supply module uses the sync control module to transmit
information to the slave power supply modules. The information may
include, but is not limited to, sync information, current sharing
information, duty cycle information, and commands. Each of the
slave power supply modules may correct any current offset or
imbalance between the master power supply module and the slave
power supply modules based on the information.
Referring now to FIG. 1, an example implementation of a current
share system 100 is shown. Although the current share system is
shown implementing DC to DC buck converters, other suitable
converters may be used. For example only, the current share system
may implement a voltage regulator module (VRM) or a linear
regulator. The current share system 100 includes power supply
modules 102, including a master power supply module 102-1 and n
slave power supply modules 102-n, where n is greater than 0 and the
current share system provides current in n+1 phases. Each of the
power supply modules 102 corresponds to a different one of the n+1
phases. For example only, the master power supply module 102-1
provides current to a buck converter 104-1 during a first phase and
the slave power supply module 102-n provides current to a buck
converter 104-n during an (n+1)th phase.
A DC power source 110 inputs DC power to the power supply modules
102 and the buck converters 104. A voltage input to the buck
converters 104 will be referred to as an input voltage (V.sub.IN)
112. The buck converters 104 may each include a switching module
116 (e.g. 116-1 and 116-n), an inductor 124 having an inductance L
and a DC resistance R.sub.L (e.g. 124-1 and 124-n), and a capacitor
(C) 128 (e.g. 128-1 and 128-n). Alternatively, the buck converters
104 may function with a single common capacitor (not shown) instead
of the capacitors 128-1 and 128-n. The buck converters 104 output
DC power to a common load 136. The voltage output by the buck
converters 104 may be provided as an output voltage (V.sub.OUT)
140, which may be provided as a feedback voltage (V.sub.FB) 142 to
each of the power supply modules 102. The current through the load
136 will be referred to as a load current (I.sub.LOAD) 144. The
master power supply module 102-1 may function with an optional
external oscillator (not shown).
Each of the switching modules 116 includes a first switch 148 (e.g.
148-1 and 148-n) and a second switch 152 (e.g. 152-1 and 152-n).
For example only, the first and second switches 148 and 152 may be
field effect transistors (FETs) as shown in the example of FIG. 1.
In various implementations, such as in the example of FIG. 1, the
first and second switches 148 and 152 may be p-type, enhancement
FETs. The first and/or the second switch 148 and 152 may be another
suitable type of switch.
In the example of FIG. 1, a source terminal of the first switch 148
is connected to the input voltage 112, and a drain terminal of the
first switch 148 is connected to a source terminal of the second
switch 152. The drain terminal of the second switch 152 is
connected to ground. A first end of the inductor 124 is connected
to a node 156 between the drain terminal of the first switch 148
and the source terminal of the second switch 152. A voltage at the
node 156 (e.g. 156-1 and 156-n) will be referred to as a switching
voltage (V.sub.SW). A second end of the inductor 124 is connected
to a first end of the capacitor 128. A second end of the capacitor
128 may be connected to ground.
The feedback voltage 142 may be measured at a node between the
inductor 124 and the capacitor 128. The switching module 116
controls connection and disconnection of the inductor 124 and the
input voltage 112. Gate terminals of the first and second switches
148 and 152 are connected to the power supply modules 102. The
power supply modules 102 control operation of the first and second
switches 148 and 152. The power supply modules 102 control first
and second switches 148 and 152 using pulse width modulation (PWM).
More specifically, the power supply modules 102 generate first and
second PWM signals 184 (e.g. 184-1 and 184-n) and 188 (188-1 and
188-n) that are applied to the gate terminals of the first and
second switches 148 and 152, respectively.
The power supply modules 102 vary the duty cycle of the first and
second PWM signals 184 and 188 to control the output of the buck
converters 104. The duty cycle of a signal may refer to a
percentage of a predetermined period (e.g., a control loop) during
which the signal is in an active state. For example only, the power
supply modules 102 may monitor the feedback voltage 142 to control
the first and second PWM signals 184 and 188 to maintain the output
voltage 140 at approximately a predetermined (e.g., commanded or
desired) voltage. The predetermined voltage is less than the input
voltage 112.
The master power supply module 102-1 transmits information
associated with the operation of the current share system 100 to
the slave power supply module 102-n. For example, each of the power
supply modules 102 controls a corresponding one of the buck
converters 104 to provide a target current. However, in some
instances, while the master power supply module 102-1 accurately
provides the target current, the slave power supply module 102-n
may provide a current that is greater than or less than the target
current, or offset from the target current. Accordingly, the
information received from the master power supply module 102-1
allows the slave power supply module 102-n to make control
adjustments to provide a current consistent with the target current
and the master power supply module 102-1.
For example only, the information transmitted to the slave power
supply module 102-n includes, but is not limited to, sync
information, current sharing information, duty cycle information,
and commands. For example only, the sync information may include a
sync pulse to synchronize phases of the power supply modules 102.
The current sharing information may indicate the target current,
which may correspond to a current through the inductor 124-1 of the
buck converter 104-1 (i.e. a master inductor current). The duty
cycle information may include a commanded duty cycle. The commands
may include power on and power off commands.
The master power supply module 102-1 transmits the information
using a single pin 194 (e.g. over a single wire). More
specifically, the master power supply module 102-1 transmits
multiple types of information, such as the sync information, the
current sharing information, the duty cycle information, and the
commands, using the single pin 194. Similarly, the slave power
supply module 102-n receives the multiple types of information
using a single pin 196. The slave power supply module 102-n
retrieves the sync information to synchronize control with the
master power supply module 102-1.
For example only, the slave power supply module 102-n may respond
to a sync pulse included in the information. Similarly, the slave
power supply module 102-n retrieves the current sharing
information, the duty cycle information, and the commands to adjust
control of the buck converter 104-n accordingly. The presence of
the connection between the single pins 196 and 194 may indicate to
the slave power supply module 102-n that the slave power supply
module 102-n is operating as a slave in a current share
arrangement. For example only, the slave power supply module 102-n
may detect the sync pulse on the pin 196 and determine that the
slave power supply module 102-n is in the current share
arrangement.
Referring now to FIG. 2, an example current share system 200
includes a master power supply module 204 and a slave power supply
module 208 shown in further detail. Although as shown in FIG. 2
only a single slave power supply module 208 is shown (i.e. in a two
phase arrangement), the current share system 200 may include any
number of slave power supply modules. Each of the master power
supply module 204 and the slave power supply module 208 includes: a
sync control module 212 (e.g. 212-1 and 212-2); a converter control
module 216 (e.g. 216-1 and 216-2); a command module 220 (e.g. 220-1
and 220-2); a reference oscillator 224 (e.g. 224-1 and 224-2); and
an inductor current measurement module 228 (e.g. 228-1 and
228-2).
The master power supply module 204 and the slave power supply
module 208 are shown to further include a current share control
module 232 (e.g. 232-1 and 232-2), which is associated with
operation as a slave in the current share system 200. The current
share control module 232-2 updates the converter control module
216-2 with current sharing information received from the master
power supply module 204. The slave power supply module 208 (and
optionally, the master power supply module 204) may be programmed
with or receive an offset 236 (e.g. 236-1 and 236-2). The offset
236 may correspond to a user calibrated or manufacturer selected
phase delay of the slave power supply module 208 with respect to
the master power supply module 204. In other words, the offset 236
may correspond to a potential offset between the circuitry of the
master power supply module 204 and the slave power supply module
208, and may reflect how quickly and efficiently the current share
control module 232-2 removes any offset and balances the
currents.
Only the current share control module 232-2 and the offset 236-2 of
the slave power supply module 208 may be active in the current
share system 200 as shown. However, it is to be understood that the
master power supply module 204 may still include the current share
control module 232-1 and receive the offset 236-1. For example
only, the master power supply module 204 may be configured to
operate as a slave in another current share arrangement.
Conversely, the slave power supply module 208 may be configured to
operate as a master in another current share arrangement.
Accordingly, the master power supply module 204 may include any
necessary components configured for operating as a slave, and the
slave power supply module 208 may include any necessary components
configured for operating as a master. As such, the master power
supply module 204 and the slave power supply module 208 may be
interchangeable.
The sync control module 212-1 communicates with the sync control
module 212-2 to provide information to the slave power supply
module 208. For example only, the sync control module 212-1
serially transmits information such as sync information, current
sharing information, duty cycle information, and commands using a
single pin or wire 240. The sync control module 212-2 serially
receives the information using a single pin or wire 244. For
example only, each of the sync control modules 212-1 and 212-2 may
implement a transmitter and receiver (i.e. a transceiver) for both
transmitting and receiving information.
The converter control modules 216 each control operation of a
respective converter (for example only, a respective one of the
converters 104 as shown in FIG. 1). For example only, the converter
control modules 216 control operation of the respective converters
104 using signals 248 (e.g. 248-1 and 248-2), each of which may
correspond to the signals 184 and 188 as shown in FIG. 1. Each of
the converter control modules 216 may include PWM time base
modules, PLLs, and/or other circuitry (not shown) associated with
PWM control of the converters 104.
The sync information allows the phases of the master power supply
module 204 and the slave power supply module 208 to be
synchronized. For example only, it may desirable for operation of
the master power supply module 204 and the slave power supply
module 208 to begin at the same time so that the respective phases
of the power supply modules 204 and 208 are aligned. Accordingly,
the sync information may include a sync pulse that indicates to the
slave power supply module 208 when to begin operation of the
converter control module 216-2. For example only, during or after
an initial power up, the sync control module 212-1 transmits the
sync pulse to the sync control module 212-2, and each of the master
power supply module 204 and the slave power supply module 208 begin
operation of the respective converter control modules 216-1 and
216-2 according to the sync pulse.
In addition to the sync pulse, the sync control module 212-1
transmits at least one second type of information to the sync
control module 212-2 using the same single wire 240. The second
type of information may include, but is not limited to, the current
share information, the duty cycle information, and the commands.
For example only, the second type of information is digital data
implementing the same digital signal structure as the sync pulse.
In other words, if the sync pulse uses a square wave digital signal
(e.g. the sync pulse is a single square wave bit), then the second
type of information is implemented using a square wave digital
signal having the same bit characteristics as the sync pulse. For
example only, the second type of information may include packetized
data (i.e. a frame of data) that is transmitted after the sync
pulse or in between consecutive sync pulses.
The digital data transmitted from the sync control module 212-1 to
the sync control module 212-2 may indicate which data corresponds
to the sync pulse and which data corresponds to the second type of
information. For example only, the sync pulse may follow a
predetermined sequence of bits (e.g. a predetermined number of 1's
or 0's). A frame of data including any of the second type of
information may immediately follow the sync pulse. After the frame
of data is transmitted, the predetermined sequence of bits may be
transmitted again to indicate another upcoming sync pulse. It is to
be understood that other suitable multiple access schemes may be
used to integrate the transmission of the sync pulse and the second
type of information using the same wire 240.
Each frame of data may include the current sharing information, the
duty cycle information, and/or the commands. Alternatively, a first
frame of data transmitted after a first sync pulse may include the
current sharing information, a second frame of data transmitted
after a second sync pulse may include the duty cycle information,
and a third frame of data transmitted after a third sync pulse may
include the commands. Some of the information (such us the current
sharing information) may be transmitted after every sync pulse,
while other information (such as the duty cycle information and/or
the commands) may be transmitted only when an update is desired. In
some situations, no information other than the sync pulse may be
transmitted. In other situations, only the duty cycle information,
the current sharing information, and/or the commands may be
transmitted. The sync control module 212-1 may transmit one frame
of data per PWM cycle of the power supply modules 204 and 208.
The sync control module 212-2 updates a duty cycle of the converter
control module 216-2 according to the duty cycle information.
Further, the sync control module 212-2 receives any of the commands
transmitted from the sync control module 212-1 and process the
commands accordingly. For example, the command module 220-1 of the
master power supply module 204 may transmit the commands to the
sync control module 212-1, which in turn transmits the commands to
the sync control module 212-2. The sync control module 212-2
transmits the commands to the command module 220-2. The commands
may include, but are not limited to, a hard shutdown command, a
soft shutdown or reset command, a run command, and an adaptive
calibration command.
Each of the power supply modules 204 and 208 further controls
operation of the respective converter control modules 216 based on
information received from the inductor current measurement modules
228. For example, in the master power supply module 204, the
inductor current measurement module 228-1 receives an inductor
current signal 252-1, which represents a current through the
inductor 124-1 (as shown in FIG. 1). The master power supply module
204 may control the converter control module 216-1 to adjust the
current through the inductor 124-1 based on the information
received from the inductor current measurement module 228-1. The
sync control module 212-1 also transmits the information received
from the inductor current measurement module 228-1 to the sync
control module 212-2 as the current sharing information.
Accordingly, the sync control module 212-2 is updated with the
current output from the master power supply module 204.
Similarly, in the slave power supply module 208, the inductor
current measurement module 228-2 receives an inductor current
signal 252-2, which represents a current through the inductor 124-2
(as shown in FIG. 1). The current share control module 232-2
receives both the information received from the inductor current
measurement module 228-2, as well as the inductor current
measurement module 228-1 via the sync control module 212-2. In
other words, because the sync control module 212-1 transmits the
current sharing information to the sync control module 212-2, the
current share control module 232-2 receives information regarding
the current outputs of both the master power supply module 204 and
the slave power supply module 208 (i.e. the currents through each
of the inductors 124). Accordingly, the slave power supply module
208, using the current share control module 232-2, may control the
converter control module 216-2 to adjust the current through the
inductor 124-1 based in part on the current output of the master
power supply module 204.
Referring now to FIG. 3, an example current share control module
300 is shown. The current share control module 300 may implement a
high speed proportional-integral (PI) control scheme to reduce any
imbalance between the current outputs of the master power supply
module 204 and the slave power supply module 208 during transient
conditions (e.g. a master inductor current and a slave inductor
current). Further, the current share control module 300 may
implement the PI control scheme to reduce any effects of output
stage resonance frequency during the transient conditions.
The current share control module 300 includes a PI control module
304 and a summing module 308. The PI control module 304 includes a
proportional module 312, an integral module 316, and a summing
module 320. The summing module 308 receives a slave inductor
current 324 and a master inductor current 328. For example only,
the received slave inductor current 324 may be a first voltage
V.sub.ind that represents the slave inductor current and the
received master inductor current 328 may be a second voltage
V.sub.target that represents the master inductor current. The
received master inductor current 328 corresponds to a target
inductor current of the slave power supply module 208. The summing
module 320 outputs a difference (i.e. error) 332 between the slave
inductor current 324 and the master inductor current 328. For
example only, a voltage V.sub.e corresponds to the error 332.
Each of the proportional module 312 and the integral module 316
receives the error 332. The proportional module 312 and the
integral module 316 calculate and output a proportional term 336
and an integral term 340, respectively, based on the error 332. The
summing module 320 sums the proportional term 336 and the integral
term 340 and outputs a current share correction 344 accordingly.
For example only, a voltage V.sub.share corresponds to the current
share correction 344. The current share correction 344 corresponds
to an output of the current share control module 232-2 as shown in
FIG. 2.
The PI control module 304 updates the current share correction 344
at a rate that is limited only by characteristics of the output
stages (i.e. the converters 104) and a sampling rate of the current
share system 200 (e.g. sampling rates of the inductor current
measurement modules 228). For example only, the current sharing
information including the master inductor current 328 may be
provided at every PWM cycle of the power supply modules 204 and
208.
In the PI control module 304 of the present disclosure,
coefficients of the PI control module 304 are selected based on
information provided via the current sharing information. In other
words, the slave inductor current 324 and the master inductor
current 328 provide information regarding the output stages of the
master power supply module 204 and the slave power supply module
208. For example only, characteristics of the PI control module 304
may be matched to an output stage resonance frequency of the
converters 104. Consequently, effects of the output stage resonance
frequency are reduced and the transient response is smoothed.
For example only, a zero z.sub.i of the PI control module 304 is
selected to match (i.e. sit on top of) the output stage resonance
frequency and a pole of the PI control module 304. Accordingly, a
gain kp.sub.share of the proportional module 312 is selected such
that the zero z.sub.i of the PI control module 304 matches the
output stage resonance frequency. A gain ki.sub.share of the
integral module 316 can be set to 1 to simplify both calculations
and hardware implementation of the PI control module 304.
For example, where
.function. ##EQU00001## z.sub.i can be isolated according to
##EQU00002## A desired value of z.sub.i is determined based on the
output stage resonance frequency wT.sub.share. The resonance
frequency wT.sub.share is calculated according to a sampling period
that corresponds to a PWM period T.sub.PWM of both the master power
supply module 204 and the slave power supply module 208, an output
inductance L, and an output capacitance C. Accordingly,
.times. ##EQU00003## and z.sub.i is selected to match wT.sub.share.
With the desired value of z.sub.i known and the gain ki.sub.share
of the integral module 316 set to 1, kp.sub.share can be further
simplified according to
##EQU00004## Consequently, the gain kp.sub.share of the
proportional module 312 can be set to match the zero z.sub.i of the
PI control module 304 to the output stage resonance frequency
wT.sub.share.
Referring now to FIG. 4, an example current share method 400 begins
at 402. For example only, the method 400 may power on the current
share system 200 as shown in FIG. 2. At 404, the method 400
determines whether a sync pulse is detected. If true, the method
400 continues with 406. If false, the method 400 repeats 404 to
continue determining whether a sync pulse is detected.
Alternatively, the method 400 may determine that a corresponding
power supply module is not in a current share arrangement if no
sync pulse is detected in a predetermined period, and terminate the
method 400. At 406, the method 400 beings operation according to
the sync pulse.
At 408, the method 400 determines whether any of a second type of
information is detected. For example only, the method 400
determines whether current sharing information, duty cycle
information, and/or commands are detected. If true, the method 400
continues with 410. If false, the method 400 continues with 404.
Alternatively, the method 400 may repeat 408 to continue to
determine whether any of the second type of information is detected
for a predetermined period before returning to 404. At 410, the
method 400 adjusts control of the current share system 200 based on
the second type of information. For example, the method 400 may
adjust a duty cycle based on the current sharing information and/or
the duty cycle information. At 412, the method 400 determines
whether to terminate the current share method 400. If true, the
method 400 ends at 414. If false, the method 400 continues at 404
to detect a next sync pulse.
The broad teachings of the disclosure can be implemented in a
variety of forms. Therefore, while this disclosure includes
particular examples, the true scope of the disclosure should not be
so limited since other modifications will become apparent to the
skilled practitioner upon a study of the drawings, the
specification, and the following claims.
* * * * *